A new medication for insomnia, Belsomra (made by Merck) has been approved by the FDA and should be available later this year. It is the first available drug to block orexin circuits in the brain. Orexin is one of several neurotransmitters which turn on the sleep-wake switch in the brain. Orexin tends to be low or missing in narcolepsy. Belsomra (generic name suvorexant) blocks the tiny receptors where orexin is supposed to act and prevents orexin from keeping you awake at night.
Of course, orexin (known also as “hypocretin” to complicate matters further) is one of many brain substances which turn off and turn on the sleep-wake switch. Others include GABA (gamma amino butyric acid), histamine, dopamine, melatonin, adenosine, glutamate, etc. Caffeine can block adenosine and keep you up; Belsomra can block orexin and keep you asleep. The effort to visualize the enormous complexities of dark and light and drowsy and alert can put you to sleep.
Belsomra (suvorexant) has been evaluated for possible habit forming issues, as well as safety risks including next morning drowsiness, sleep driving, and sleep eating. We should also be hearing more about narcolepsy (orexin deficiency), which in its milder form shows itself as excessive daytime sleepiness (EDS) and can be treated with scheduled daytime naps. However, narcolepsy is relatively uncommon- one in two thousand people.
When I have had a chance to prescribe and have more experience with this medication I will update you further.
Ross F. Grumet, MD / The Sleep Advocate